relic helmet rust removal

[General Patton]

Hello everyone
I have a relic ww2 german helmet that is caked in rust. I want to remove as much rust as possible because I see original green paint undernethe the rust. I think I want to soak the helmet in soap water for a while then rub it off with a rag. The problem is a bit of the liner is still intact and super hard and stiff. If I soaked the helmet completely in soap water, would the liner be affected by the soap water? I want to protect it as much as possible. Also could a wire brush be used after the soak? Thank you for the help!

[General Patton]

here are some pictures of my helmet...

[ph3s]

The best way would be electrolysis

Dailymotion - How to Remove Rust with Electrolysis - a Life & Style video